Aqueous explosive compositions having reversible fluent-nonfluent properties

ABSTRACT

AQUEOUS EXPOSIVE COMPOSITIONS HAVING A DENSITY OF 1.8 GRAMS/CC. OR GREATER AND HAVING REVERSIBLE FLUENT-NONFLUENT PROPERTIES ARE PROVIDED. THESE AQUEOUS EXPLOSIVE COMPOSITIONS EMPLOY METAL PERCHLORATES, CAPABLE OF FORMING A HYDRATE WITH WATER, AS THE OXIDIZER. FLUENT-NONFLUENT REVERSIBILITY IS ACHIEVED BY PROCESSING THE AQUEOUS COMPOSITIONS AT TEMPERATURES ABOVE THE TEMPERATURE AT WHICH A HYDRATE OF THE PERCHLORATE WILL DISSOCIATE RELEASING WATER ENABLING PREPARATION OF A FLUENT EXPLOSIVE SLURRY COMPOSTION. THE FLUENT EXPOSIVE SLURRY COMPOSITION IS THEN COOLED TO A TEMPERATURE AT WHICH A HYDRATE FORMS AND THE PREVIOUSLY RELEASED WATER IS COMBINED WITH THE METAL PERCHLORATE AS A HYDRATE FORMING A NONFLUENT EXPLOSIVE SLURRY COMPOSITION.

R. H. EVANS 3.684,594 AQUEOUS EXPLOSIVE COMPOSITIONS HAVING REVE'RSIBLE Aug 15, 1972 FLUENT-NONFLUENT PROPERT I ES Filed May 15, 1970 RICHARD H. EVANS INVENTOR ATTORNEY United States Patent C) 3684,594 AQUEOUS EXPLOSIVE COMPOSITIONS HAVING REVERSIBLE FLUENT-NONFLUENT PROPERTIES Richard H. Evans, Cumberland, Md. assignor to Hercules Incorporated, Wilmington, De]. Filed May 15, 1970, Ser. No. 37,615 Int. Cl. C06b 1 00 U.S. Cl. 14938 12 Claims ABSTRACT OF THE DISCLOSURE Aqueous exposive compositions having a density of 1.8 grams/ cc. or greater and having reversible fluent-nonfluent properties are provided. These aqueous explosive compositions employ metal perchlorates, capable of forming a hydrate with water, as the oxidizer. Fluent-nonfluent reversibility is achieved by processing the aqueous compositions at temperatures above a temperature at which a hydrate of the perchlorate will dissociate releasing water enabling preparation of a fluent explosive slurry composi tion. The fluent exposive slurry composition is then cooled to a temperature at which a hydrate forms and the previously released water is combined with the metal per chlorate as a hydrate forming a nonfluent explosive slurry composition.

This inventon relates to a new class of high energy, high density explosive compositions comprising water, a metallic perchlorate capable of forming a hydrate with water, and a moderate amount of a fuel and/ or sensitizing agent. In another aspect ths inventon relates to the process for preparing high energy, high density explosive compositions which have reversible fluent-nonfluent properties as a result of hydrate formation and dissociation.

Explosive compostions of the slurry type employing an inorganic oxidizer salt as the oxidizng agent have had wide use in the explosves industry in recent years. These compositions are generally comprised of an inorganic oxidizer salt, water, a sensitizing agent, and a thickening agent. The thickening agent is employed in an amount sufficient to impart consistency to the slurry and to prevent settlng of any of the various solid ingredients in the slurry. In many norganic oxidizer salt compositions, the principal oxidizer salt employed is ammonium nitrate. The exposives art has long recognized that other inorganic oxidzing salts and in particular, metal perchlorates, are effective oxidizing agents. Metal perchlorates have been employed in limted quantities in explosive compositions prncipally because in dry form and mixed or in contact with fuels, the perchlorates are hazardous, being particularly sensitive to shock, friction and heat. The explosives art has also recognized the advantages of explosive compositions that can be processed as a fluent slurry and then converted into a stable nonfluent composition after uniform mixing of the composition has taken place and the slurry has been transferred to a suitable receiving means. In order to achieve ths result, gelling agente, thickening agents and polymers are commonly added to slurry oom positions to convert the slurry from the fluent to the nonfluent state. Other means of converting exposive compositons both commercial and military from the fluent to the nonfluent state depend upon crystalline melting or freezing, upon changed solubility of products with temperature or upon the viscosity changes with temperature.

It is an object of this inventon to provide an explosive composition employing metal perchlorates as the oxidizing agent which can be safely processed as a fluent aqueous slurry and which can be converted to the nonfluent state without the necessity of using gelling agente, thickening agents, or crosslnkable polymers and crosslinking agente.

It is another object of this inventon to provide explosive slurry compositions having high energy densities which can be converted from the fluent to the nonfluent state as a result of hydrate formation and dissociation.

Other objects of ths inventon will, in part, be obvious and will, in part, appear hereinafter. For a complete understanding of the nature and objects of this inventon, reference is made to the following detailed description.

In accordance with ths inventon an aqueous explosive composition is provided having a density of at least 1.8 grams per cc. said explosive composition comprising a metal perchlorate oxidizer selected from the group consisting of sodium perchlorate, lithium perchlorate, magnesium perchlorate, strontium, perchlorate, calcium perchlorate, aluminum perchlorate, and mixtures thereof; water, and a metal fuel and/or a sensitizing agent, said explosive composition comprsing by weight from about 25% to about of a metal perchlorate oxidizer, from about 3% to about 15% water, from about 0% to about 40% metallic fuel, and from 0% to about 60% sensitizing agent. The cumulative total of metallic fuel and senstizing agent in the explosive composition of this inventon comprises at least about 20% by weight of the composition. The ratio of metal perchlorate oxidizer to water in the explosive composition is mantained within the compositional range in which substantially all the water in ex plosive composition can be chemically bound to the metal perchlorate when the metal perchlorate is converted from ts state of: hydration in the fluent slurry to a higher state of hydration by a reduction in the temperature of the slurry.

The explosive compositions of this inventon are prepared by a process which has as ts first step the admixing, of water and a metal perchlorate oxidizer which will form a hydrate with water at a temperature above the dissociation temperature of a hydrate which will form upon cooling and at which temperature there is provided suflcient uncombined water permitting addition of solid i11- gredients to the admixture to form a uniform and fluent slurry composition. The fluent slurry is stable to settling of solid ingredients since it has a high density of about 1.8 grams per cc. or above which eiectively prevents settling out of solid ingredient additives employed. The resulting homogeneous and fluent explosive compositions is transferred to a suitable receiving means and co0led to a temperature at which the metal perchlorate hydrate forms a higher state of hydration than ts state of hydration during mixing whereby a nonfluent explosive composition is formed. In the process of this inventon some metal perchlorate can be and usually is dissolved in the water during the mixing process. Thus, in the case of sodium perchlorate, mixing of solid ingredients is generally carried out with most of sodium perchlorate in solution in water. In this condition the sodium perchlorate is in a non-hydrated state. Cooling of the admixture to below the dissociation temperature of sodium perchlorate monohydrate permits the water in the admixture to be chemically combined whereby the slurry is converted to the nonfluent state. In the case of a metal perchlorate where more than one state of hydration exists such as lithium perchlorate or aluminum perchlorate, it can be necessary to cool the fluent slurry to a temperature which is below the dissociation temperature of one or more of the pessible hydrates of the perchlorate in order to combine substantially all the water present so that a nonfluent slurry results. The hydrate dissociation temperature is the minimum temperature at which the hydrate loses or starts to lose ts water of hydration. Hydrates often do not have sharply defined dissociation temperatures and often dis sociate over a temperature range.

The foregoing process can also be described with reference to FIGS. 1 and 2 in which FIG. 1 is a phase diagram of the system sodium perchlorate-Water and FIG. 2 is phase diagram of the system lithium perchlorate-water. In the system sdium perchlorate-water the principal hydrate of sodium perchlorate that forms is sodium perchlorate monohydrate. Thus when preparing explosive composi- The following examples more fully illustrate ths in vention. A11 parts and percentages are by weight unless otherwse specified.

EXAMPLE 1 tions of this invention employing the sodium perchlorate 5 water system it is necessary to maintain the temperature Ab0l1t 35 parts of Sodlum perchlorate, and 19 parts of of the aque0us slurry composition of sodiurn perchlorate Water are added to a P% yp IIJXGI' and mxed Y above the dissocaton temperature of sodium perchlorate at The Water dlsolves P 85% Sodlum monohydrate. In this system mixing of the slurry is carried PeTchl'ate the l'esullllg admlifll"e f= P 1Slng a fll}ellt out with the sodium perchlorate present in an unhydrated 10 slurry of S0dlum pef chlol'ae Partlcles 111 aquells S0dlum state. When employing the lithium perchlorate-water sys- P" 01111011 1S added parts of cycotflljlethyl tem to prepare the explosive compositions of this invenefletr{lltral llfle 311d parts of Pftlclllate tion it is generally preferable to mix water and the lithium alummum 111 Wh1ch at of partl cles are perchlorate at a temperature above the dissociation tem- Smaller than 44 ImG}'OIJS largest 1111161151011 The perature of lithium perchlorate trihydrate. Thus, the solid 15 Y p malltallled at f abov6 ingredients can be admixed to form a fiuent slurry in durlng the eIlt ll'e mlxlllg P The aql leolls P which the lithium perchlorate is present as a monohydrate. P1Ovldes Suflclent hquld mamtau the It is necessary to provide sufiicient water in this comadmlxture the of a fluent exploslve comPosl tlon position so that the lithium perchlorate monohydrate and sufl clent II11X1118 the fluellt GXP OSIV COIIIPOSIOII uncombined water provde suflcient liquid to permit dis- 15 Poured polyeth ylene bag and cooled persing of the desired amount of solid ingredients through perature below the sod1um perchlorate-hydrate rirssoc1aout the slurry durng mixing. The mo t f f water t1on temperature. Under these temperature COIIS.IIOIJS, the in the slurry composition is within the limits of water f Pf chemlcauy bmds the waterm the which can be combined with the lithium perchlorate when Posmo1 m form of a monohydrate Th1s the lithium perchlorate is converted from the monohydrate hydrate f9rmatlon removes the water fr0m the flunt to the trihydrate upon cooling t0 the dissociation temperaslurry Y" result that a nonfiuent explosve ture of the trihydrate or below. composmon formed Table I below contans a listing of metal perchlorates A Small charge nonfluent eploslve P which can be employed in this invention, the predominate descr Example 1 15 tested hydrates which will form with these metal perchlorates, a and 1mtratron s ensltivrty. The test valu es are W1thm limits mixing temperature zoneinwhich the perchlorate-hydrates nor{nany cqnsldered safe for Processmg Results of the lose their water of hydration and in which temperature testmg gwen below zone a fluent slur composition can be formed, and a dssociation tempeture for the perchlorate hydrates at r lmpict of a 2 kilogram drop which temperature or below the perchlorate will form the t a e1g f hydrate designated and in which temperature range a shgmg fnctlon tst 0 reactlon to g at 8 nonfluent slurry can be formed in accordance with ths Th eet i g? at a invention. For almost al1 applicatons of the slurry com- S 1 1 0 5100 positions and process of this nvention the slurry will be cntlca dlameter .l' Inch eionatlori rate cooled to a temperature below the dissociation temperameters/se.c'.Detonatlon 1s accomphshedwlth a bl?stmg ture of the perchlorate hydrate in its highest state of hycap contammg g,ram of p?ntaerythntol tetramtrate' dration to convert the slurry from a fluent to a nonfluent Petonatlon Propagatlon mm 15 measured and the rate condition 1s 5100 meters/second.

TABLE I EXAMPLES 2-7 temp s t r The following examples illustrate additional explosive Metalpmhomte hydmte C rangecc' compositions of this invention. These compositions are NaCIO4.H2O' 50 prepared following the procedure set forth in Example 1 88z? 93 5; 50 with the exception that the processing temperature at which these compositions are mixed varies as specified in s0100 Tabla 85-100 85 86-125 A.1(C10|)3.15H20 75 77-80 *A trihydrate of sodium perchlorate is known hut: is generally een sidered unstabl0.

TABLE II Example Number 2 3 4 5 6 7 Composition, wt; percent aC1O4 H20 (pH 5.0) 10 6 10 10 10 10 Formamide 2 Mixing temperature, C. (fluent slurry)-.--. 95400 95-100 70 70 70 70 Coolmg temperatura, C. (non-fluent slurry)- 93 295 250 250 250 250 Critica] diameter (inches) 2.0 1.0 1. 0 Detonatlon rate (meters/sec.) 5, 500 6, 200 5, 850

1 Cyc1otrimethylenetrinltramine (Type E). 2 Cyclotetrmnethylenetetranltramine (Class B).

The explosive composition of Example 2 is a fluent mixture between 95 and l C. This composition solidifies with the formation of the trihydrate of lithium perchlorate at a temperature of 93 C. or below, see FIG. 2. In this example it is not believed that the monohydrate of sodium perchlorate takes part in the hydrate hardening of the mixture since the water in the mixture is utilized prncipally in forming the trihydrates of lithium perchlorate and possibly some monohydrates of lithium perchlorate at temperatures above the dissociation temperature of the sodium perchlorate hydrate, see FIG. 1.

The explosive composition of Example 3 is a fluent slurry between 95 and 100 C. laut hardens on cooling below 95 C. to a nonfluent slurry where the di, tetra and other hydrates of strontium perchlorate are formed.

The explosive composition of Exarnples 4-7 are all fluent above 70 C. and harden upon cooling to 50 C. or below to a nonfluent slurry as a result of the sodium perchlorate-hydrate formation. No attempt is made to detonate the explosive composition of Example 4 but the explosive compositions of Example 5 detonates at a diameter of less than about 20 inches, and the explosive composition of Examples 6 and 7 detonate at a diameter of less than 1.0 inch.

The metal perchlorates which can be employed in the explosive composition of this nvention are all capable of forming one or more hydrates with water. When preparing the fluent-nonfluent compositions of this nvention it is necessary to maintain the perchlorate-water ratio within a compositional range within which a hydrate will form in 0rder to take advantage of hydrate formation to acheve heat reversible fluent-nonfluent compositions. This compositional range varies with different metal perchlorates depending on the predominate hydrates which can be formed which hydrates are set forth in Table I. Metal perchlorates can be added to water in forming a fluent slurry as either anhydrous or hydrated salts. In generals, particle size of the metal perchlorates can range from about 10 to about 200 mesh (U.S. Standard Sieve Series).

High energy metallic fuels which can be employed 11'! the explosive composition of this nvention include metals and alloys of metals. Illustrative materials of this class include aluminum, boron, magnesium, silicon, titanium, zirconium, and alloys such as ferrcsilicon, aluminum/ magnesium, silicon carbide, and the like. These metallic fuels are generally employed as small particles havmg a particle size range from about 7,1. to about 50/L. A preferred high energy metallic fuel for use in the explosive composition of this nvention is aluminum. When employing aluminum in these compositions it is preferable to maintain the water admixed in the slurry composition at a pH of about 6.0 or below and preferably at a pH of about 5.0 or below. By making the water slightly acidic the metallic aluminium remains passive to attack water present within the composition with the result that the compositions are stable for long periods of time.

When employing a metallic fuel such as magnesium, it is preferable to employ an alkaline buffer in the water, which passivates the magnesium trom attack by water present within the composition. Other means to passivate metals such as coating of the metals employed to prevent attack of the metals by Water are known and generally can be employed as long as the passivating material is compatible with the ingredients of the explosive cornposition.

Senstizng agents which can be employed in the explosive composition of this nvention include pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT), cyclotrimethylenenitramine (RDX) cycloetramethylenetetranitramine (HMX), nitrophenols, and the like.

The explosive composition of this nvention can optionally contain from 0% to about 5.0% of an organic fuel which functions as both a solvent for the metal perchlorate and as a sensitizing agent. The organic fuels which can be employed are solvents for the metal perchlorate salts and will form a solid solvate with the metal perchlorate salts. Illustrative solvents for the metal perchlorate oxidizer salts of this nvention include low molecular weight amines such as ethylamine, propylamine, butylamine, pentylamine, cyclohexylamine, mixtures thereof, and the like; amides such as formamide, dmethylformamide, acetamide, urea, N-methyl prcpionamide, N-ethyl proponamide, N-propylpropionamide, acetanlide, mixtures thereof, and the like; polyhydric alcohols, ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, polyethylene glycol monoethylether, polyethylene glycol dimethylether and the like.

The explosive compositions of this nvention can be employed as blasting agents, as conventional explosives and as military explosives. When employed as a blasting agent these compositions can be stored in polyethylene bags and used for blasting in dry or wet bore holes. The explosive compositions of this nvention are particularly useful in military explosives. These compositions can be mixed, charged to a munition and cooled to a homogeneous solid explosive mass. If desired, these compositions can be removed from a munition by heating the munition to a temperature above the hydrate dissociation temperature of the explosive at which temperature water will be released from the hydrate permitting the explosive composition to be removed from the munition.

In the explosive compcstions of this nvention the water solvent replaces relatively non-energetic carbonaceous fuels and allows for a larger incorporation of high energy metal fuels, thus increasing the overall energy of the explosive. The increased energy density and inherently lower costs of these solvated perchlorate explosive make these explosive compositions highly advantageous particularly where it is desirable to convert the slurry from the fluent to nonfluent state and vice versa.

What I claim and desire to protect by Letters Patent is:

1. An explosive composition having a density of at least 1.8 grams per cc. said explosive composition consisting essentially of bv weight trom about 25% to about 90% of a metal perchlorate oxidizer selected from the group consistng of sodium perchlorate, lithium perchlorate, lithium perchlorate, magnesium perchlorate, chlorate, magnesium perchlorde, strontium perchlorate, and mixtures thereof; from about 3% to about 15% water, from about 0% to about 40% metallic fuel, and from 0% to about 60% organic senstizing agent, the cumulative total of metallic fuel and organic sensitizing agent in the composition comprising at least 20% by weight of the composition, and the ratio of metal perchlorate oxidizer(s) to water in the explosive composition being within the compositional range in which substantially all of the water in the explosive composition is chemically bound to the metal perchlorate(s) in the form of a perchlorate-hydrate(s) at a temperature below a dissociation temperature of the perchlorate hydrate(s) t which temperature said explosive composition is nonuent.

2. The explosive composition of claim 1 containing from 0% to about 5.0% of organic fuel solvent.

3. An explosive composition having the density of at least 1.8 grams per cc. said explosive composition consisting essentially of sodium perchlorate, water, a metallic fuel, and a sensitizing agent, said composition comprising by weight from about 25 t0 about sodium perchlorate, from about 6% to about 15% water, from about 5% to about 40% metallic fuel, and from about 2% to about 60% sensitizing agent, the cumulative total of metallic fuel and sensitizing agent in the composition comprising at least 20% by weight of the composition,

and the ratio of metal perchlorate oxidzer to water falling within the compositional range in which sub 7 stantially all of the water in the slurry can be chemically laound to the sodium perchlorate in the form of a hydrate.

4. The explosive compositon of claim 3 in which the metallic fuel is aluminium and in which the sensitizing agent is cyclotrimethylenetrnitramine.

5. The explosive compositon of claim 4 contaim'ng from about to about 5.0% organic fuel solvent.

6. The process of preparing as explosive compositon consisting essentially of by weight rom about 25% to about 90% of a metal perchlorate oxidizer, selected from the group consisting of sodium perchlorate, lithium perchlorate, magnesium perchlorate, strontium perchlorate, calcium perchlorate, aluminum perchlorate, and mixtures thereof, from about 3% to about 15% water, from about 0% to about 40% metallic fuel, and from 0% to about 60% crganic sensitizing agent, said process comprsing:

(a) admixing water and a metal perchlorate oxidizer at a temperature above a dissociaton temperature of a hydrate which can be formed from the water-metal perchlorate admixture to form a fluent slurry,

(b) while maintaining the temperature of the slurry above the dissociaton temperature of a perchloratehydrate which can be formed, admixing metallic fuel and organic sensitizing agent to the fluent slurry in an amount such that the cumulatve weight of these components comprises at least 20% by weight of the resulting slurry compositon, said resulting slurry being homogeneous and fluent,

(c) transferring said fluent explosive compositon into a receiving means, and

(d) cooling the explosive compositon to below the dissocation temperature of the perchlorate hydrate at which temperature the fluent slurry is converted to the nonfluent state.

7. The process of claim 6 in which the metal perchlorate oxidizer is sodium perchlorate, the temperature of admixing water and sodium perchlorate oxidizer is above 50 C. the resulting explosive compositon being cooled to a temperature below about 50 C. to form a nonfluent compositon.

8. The process of claim 6 in which the metal perchlorate oxidizer is the lithium perchlorate, the temperature of admixing water and lithium perchlorate is between about 95 C. and 100 C., the resulting explosive composition being cooled to a temperature below about 93 C. to form a nonfluent explosive compositon.

9. The process of claim 6 in which the metal perchlorate oxidizer is magnesium perchlorate, the temperature of adrnxing water and magnesium perchlorate is between about C. and 100 C. the resulting explosive composition being cooled to a temperature below about 80 C. to form a nonfluent explosive compositon.

10. The process of claim 6 whereiu the metal perchlorate oxidzer is strontium perchlorate, the temperature of admixing water and strontium perchlorate is between about 95 C. and 0., the resulting explosive compositon being cooled to a temperature below about 95 C. to form a nonfluent explosive compositon.

11. The process of claim 6 wherein the metal perchlorate oxidzer is calcium perchlorate, the temperature of adrnixing water and calcium perchlorate is between about 85 C. and 100 C., the resulting explosive compositon being cooled to a temperature below about 85 C. to form a nonfluent exposive compositon.

12. The process of claim 6 wherein the metal perchlo rate oxidzer is aluminum perchlorate, the temperature of aclmixing water and aluminum perchlorate is between above 77 C. and C., t he resulting explosive composition being cooled to a temperature below about 75 C. to form a nonfluent explosive compositon.

References Cited UNITED STATES PATENTS 3,113,894 12/1963 Bul't0rl 14942 X 3,238074 3/ 1966 Griflith et al. 149-42 X 3,345224 10/1967 Griflith 14956 X 3,190777 6/1965 Breza et al. 149-77 X 3,282,753 11/1966 Cook et al 14977 X 3,574,011 4/1971 Knight 149-42 X BENJAMIN R. PADGETT, Primary Examiner S. J. LECHERT, JR., Assistant Examiner U.S. C1. X.R.

Patent No. 3 594L Dated August 15, 1972 Inventor(s) Richard H., Evans (Case l) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column l, line 1 of the Abstract of Disclosure Page 1, line 1 of the Abstract of Disclosure exposive should :cead explosive Column l, line 60 of tlie printed patent Page 2, line 31 of the application, expos ive should reed explosive Column 3, Table 1 last column corresponding to Page 6 of the application, l2l-l70 86-125 and 77-80 should read 121-175 86-120 and 77-85 Column 4, Table II opposite "Cooling 'I'emperature,

C. (non-fluent slurry)" corresponding to Page 9 of the application, "2 93, ;95 50 50, 1350, 50 should read g 93, 95,250, Z50, 250,250

Column 5, line 56 of the printed patent Page 11, line 16 of the application,v insert by between attack water In the Claims, Column 6, Claim 1, line 46 delete lithium perchlorate Claim 1, line 47, delete chlorate, magnesium perchloride, Claim 1, line 47 after "strontium Perchlorate, insert calcium perchlorate, aluminum perchlorate,

Column 7, Claim 4, line 4, aluminium should read aluminum- UNTED smms PA'EENT FFECE Patent No. 3684594 Datd August 15,, 1972 Inventor(s) Richard o E H (Case 1) 4 2 It is certified that error appears in the abore-identified patent and that said Letters Patent are here'by corrected as shown below:

Column 7, line 8, Claim 6, as shoull reac Column 8, Claim ll, line 21, exposive should read explcsive Column 8, Claim 12, line 25, above should read about Signed and sealed ths 9th day of January 1973.,

(SEAL) Attest:

EDWARD M.FLETCHERJR. ROBERT GOTTSCHALK Commssoner of Patents Attesting Officer 

